The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structures.
In the past, the semiconductor industry utilized various methods and structures to form control circuits for light emitting diodes (LEDs). Some LED controllers utilized a P-channel metal oxide semiconductor (MOS) transistor that was connected in a high-side configuration in order to regulate the value of a voltage applied to the LED. The P-channel MOS transistor generally resulted in larger die sizes which increased the costs.
In other configurations, an N-channel MOS transistor was connected in a low-side configuration to control the LED. The low-side configuration connected the load to the power supply. If the output of the low-side configuration accidentally became shorted to another connection, large currents could flow through the load and damage the load. One example of an LED controller that uses an N-channel transistor connected in a low-side configuration is described in the data sheet of a part referred to as the LP3936 that was available from National Semiconductor of Santa Clara, Calif.
Accordingly, it is desirable to have an LED controller that connects the load via a high-side switch configuration, that does not use a P-channel transistor to control the load, and that has a lower cost.
For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action. For clarity of the drawings, doped regions of device structures are illustrated as having generally straight line edges and precise angular corners. However, those skilled in the art understand that due to the diffusion and activation of dopants the edges of doped regions generally may not be straight lines and the corners may not be precise angles.